<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script type="text/javascript">
			// var x=10;
			// console.log(x);
			// {
			// 	var x=100;
			// 	console.log(x);
				
			// }
			// console.log(x);
			let x=10;
			console.log(x);
			{
				let x=100;
				console.log(x);
			}
			//代码中let定义变量作用域,代码段结束,里面的x也结束
			console.log(x);
			//js只有变量没有常量定义.es6定义常量
			// const sysname="学生管理系统";
			// console.log()
			const PI=3.14;
			console.log(PI);
			PI=3.1415926;
		</script>
	</head>
	<body>
		<h3>箭头函数,新标准</h3>
	</body>
	<script type="text/javascript">
		//js函数,无参
		var js0=function(){
			console.log("js0,无参");
		}
		js0();
	</script>
</html>
